Discharge gap



Feb. 4-, 1941. R, M. PARTlNGTON 2,230,727

DISCHARGE GAP Filed Aug. 19, 1939 Inventor- Robert, M. Parti gton,

by A

His Attorney.

Patented Feb. 4, 1941 UNITED STATES DISCHARGE GAP Robert M. Partington,New Lebanon, N. Y., assignor to General Electric Company, a corporationof New York Application August 19,

3 Claims.

My invention relates to discharge gaps and more particularly todischarge gaps of the horn type. A discharge gap may be connected acrossvarious kinds of electrical apparatus such as 5 condensers andtransformers to protect the apparatus from excess voltages. Aconventional horn gap as used in the past has included two hornelectrodes accurately spaced at their lower ends to provide a gap whichwill arc-over when the voltage between them reaches a predeterminedvalue, the are serving to short circuit the apparatus across which thegap is connected so as to prevent appreciable rise of voltage above thatat which the gap has arced over. The electrodes of the conventional horngap extend upwardly and diverge from each other so that the spacebetween them gradually increases until it reaches a maximum at theirupper ends. After an are forms between the bases of the electrodes wherethe spacing is a minimum, the arc will rise between the electrodes untilit reaches their upper tips where the spacing is a maximum, the arebeing forced upwardly by a magnetic action and also because thetemperature of the are is far i above the surrounding air. The currentflowing in the arc also flows in both electrodes so that this currentsurrounds the restricted space between the electrodes and creates aconcentrated magnetic field which tends to force the are upwardly evenafter it reaches the upper tips of the electrodes. This action willforce the center of the are above the tips of the electrodes until theare is finally so long that the voltage can no longer maintain it and itgoes out. If the voltage 35 has not decreased, an arc will again strikebetween the base portions of the electrodes and this cycle will berepeated indefinitely until the voltage has been reduced below thatnecessary to break down the gap at the base of the electrodes. Thisrepeated striking of the are at the base of the electrodes soon burnsthe surfaces of the electrodes at this point and changes thecharacteristics of the gap so that it may not give the desiredprotection for the apparatus across which it is connected. It isobviously desirable that the arc should persist after it has reached theupper tips of the electrodes until the voltage has been reduced belowthat which will cause the arc to restrike between the bases of theelectrodes.

50 This will greatly reduce the injury to the arcing surfaces betweenthe bases of the electrodes and greatly prolong their useful life.

The general object of the invention is to provide a discharge gap of thehorn type having such characteristics that an are which may reach a1939, Serial No. 291,103

position between the upper tips of the electrodes will persist until thevoltage has been reduced sufficiently to prevent restriking of the arebetween the bases of the electrodes or at least to delay theextinguishment of the arc and greatly reduce the frequency at which itwill restrike between the bases of the electrodes as compared with itsaction in a horn gap of the conventional type.

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawing in which the singlefigure shows a horn gap constructed in accordance with the invention andconnected across a condenser to protect the condenser from the effectsof excess voltage, the condenser being shown diagrammatically. In thedrawing the gap is shown rotated ninety degrees counterclockwise fromits position when in use.

The horn gap ill shown in the drawing is connected across a capacitor llbetween two terminals l2 and I3. The horn gap 10 includes two horns I4and 15 connected respectively to the two terminals l2 and i3 andadjustably secured in place by the clamps l6 and 11. Each electrodeincludesa base portion I8 accurately spaced at their adjacent ends toprovide a protective gap [9 proportioned to arc-over when the voltage between the electrodes reaches a predetermined maximum value beyond whichit would be apt to injure the condenser H. The intermediate portions 20of the electrodes diverge upwardly from the protective gap I9 and theirupper ends or tips 2i extend toward each other to provide a gap 22 whichis somewhat longer than the protective gap H) but considerably shorterthan the distance between the adjacent upper parts of the intermediateportions 20 of the electrodes l4 and I5. I

If the voltage across the condenser II increases and approaches adangerous value, it will cause an arc to strike across the protectivegap IE) to protect the condenser. This are will rise between theelectrodes 14 and I5 under the influence of its heat and the magneticfield surrounded by the current in the arc and in the portions of theelectrodes below the arc. As the arc rises it becomes longer and longeruntil it reaches the upper ends of the intermediate portions 20 of theelectrodes, finally decreasing as it reaches the upper gap 22 where thelength of the arc will be somewhat greater than at the protective gapl9. The heated condition of the are at the gap 22 tends to cause the arcto rise into an upwardly curved position but the magnetic 55 fieldproduced by the arc current between the sides of the electrodes is verymuch less than in the Conventional horn arrester because the spacebetween the intermediate portions 20 of the horns is much greater andthe magnetic field much less concentrated under the arc. An are havingonce reached the upper gap 22, therefore, tends to persist if the gap 22is properly proportioned until the voltage between the-terminals l2 andI3 has decreased to such a value that it cannot cause the arc torestrike across the gap 19 if it should be extinguished at the gap 22.Even if the arc should be extinguished at the gap 22 before the voltagecan cause it to restrike at the gap l 9, this action will be very muchretardedas compared:

with that of the conventionalhorn gap so that restriking of the arc atthe protective gap l9 will be much less frequent and injuryto-the arcingsurfaces of the electrodes at this gap l9 much reduced.

The electrodes Hand 95 may be formed of any suitable metal such ascopper and a plating of chromium has been found to be of advantage inpreventing corrosion and in prolonging the life of the arcing surfacesof the electrodes. Electrodes formed of round, copper wires or rodsabout inch in diameter have given excellent results as good as or betterthan those secured by the use of conventional sphere gaps and a horn gapconstructed in accordance with the present invention is obviously muchsimpler and more economical than a sphere gap. Parts of the horn gapsubject to deterioration from effects of the arc are also inexpensiveand may be easily and quickly replaced. If the arc currentisfound toexceed more than about 60 amperes, it maybe desirable to use hornssomewhat largerthan 4 inch in-diameter.- The tendency of the-arc topersist after it reaches the-upper gap-.22 provides adequate time forany ionized air produced initially by the arc at the gap [9 to'becarriedaway from this protective gap I9 andthus help to preventrestriking of the arc-after the voltage has decreased below it normalrestrike value.

' The invention has been explained by describing and illustrating apreferred embodiment thereof,

but it will be obvious that changes may be made without departing fromthe spirit of the invention and the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of theUnited'States, is:

1. An electrical discharge gap including electrodes spaced to provide aprotective gap, the electrodes extending upwardly from said gap anddiverging from each other, and the upper ends of the electrodes finallyextending toward each other to provide a second gap longer than saidprotective gap but shorter than the distance between the adjacent upperparts of said diverging portions.

2'.'An electrical discharge gap including electrodeshaving base portionswith their adjacent endsspaced to form a protective gap, intermediateportions diverging upwardly from said base portions, and-upper endportions extending toward each other from said intermediateportions-toform a second gap longer than said protective gap but shorterthan the adjacent upper parts of said intermediate portions 3. A voltagelimiting arc gap for capacitors comprising, in combination, a pair ofelectrodes in air spaced to form a calibrated discharge gap whicharcs-over at a predetermined voltage, metal arms extending upwardly fromsaid electrodes in a vertical plane and diverging from each otherwhereby an are between said electrodes will rise vertically under thecombined influence of the heat ofthe arc and the magnetic action of thecurrent and will be drawn out by the divergence of said arms, and asecond gap formed between the upper extremities of said arms, saidsecond gap having a maximum spacing which is less than the spacingbetween the upper extremities of said arms, said arms being of suchlength and divergence that an arc rising between them will transfer tosaid second gap and remain there without restriking across thecalibrated gap if the voltage does notfall below the arc-over voltageofthe calibrated gap, said second gap having a minimum spacing; which issufiiciently greater. than the spacing, of said calibrated gap tocausean arc across said second gap to clear at a voltage lower than thearc-over voltage of said calibrated 1 ROBERT M. PARTINGTON.

